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If you search along the weedy
margins of the railroad track you cross just before you enter the refuge, any time between
May and August, you'll probably find one of the most interesting flowering plants and
plant-herbivore systems in the southeast, Passiflora incarnata, commonly called
maypops or simply passion vine. They also occur along the margins of the
dikes in some areas, especially along the east side of Pool 1.

Passion vines produce
beautiful, large flowers that are easy to find once they open. These large, complex
flowers open quickly at about 11 a.m., and last only one afternoon before shriveling and setting
fruit.

Passion vine is chemically protected by
cyanogenic glycosides, which prevent most plant-eating insects from feeding on it.
It is, however, fed upon by the larvae of two specialized butterflies, which feed on no
other plants.

This is Agraulis vanillae, the
gulf fritillary. These butterflies are often present in large numbers, especially
from mid-late summer. Adults can usually be found in the vicinity of passion vines,
and the plants themselves often have several larvae per plant. Gulf fritillary
caterpillars are more often found on passion vines in open, full sun, and are usually
found feeding on older leaves away from the tip of the vine.

These are the eggs and larva of
the zebra longwing, Heliconius charitonius. These butterflies lay their eggs in
clusters at the very tip of the growing vine, and are more often found on plants that are
at least partially shaded. Thus, the two species of butterflies seem to avoid direct
competition by feeding on different parts of the plants, and selecting different
microhabitats.

Reproductive behaviors of adult
Heliconius are amazing. An hour or two before female butterflies eclose
(emerge)
from their pupae, they release pheromones to attract males. Males attempt to monopolize
the pupa by jostling with each other (left) until all but one of the males is driven
off. The victor hangs around to await the emergence of the female. Nothing
too unusual, right?

As it turns out, this randy
little bugger can't wait. He somehow penetrates the exoskeleton of her pupa with the tip of
his abdomen before she even emerges. They begin mating while
she is still inside. As she emerges from her pupa, and begins to unfold and dry her
wings (right), the pair is already in copula. This behavior is uncharitably
called "pupal rape".

The butterflies and caterpillars are
relatively easily found when they're present, which is usually for most of the summer and
early fall. The reproductive behaviors of Heliconius will be tougher
to observe;
the females seem to normally emerge early in the morning, so if you're in the vicinity of
passion vines where Heliconius caterpillars can be found, look on surrounding
vegetation for pupae. The combative jostling of a couple of males around a little
brown lump is a sure sign that these cool behaviors are about to begin.